Eocene tavda formation clays: Lithogeochemical and sedimentological aspects (kyshtyrlinskoe deposit, west Siberia)

Abstract

© 2019 Tomsk Polytechnic University, Publishing House. All rights reserved. Relevance. Mineral composition of Tavda formation clays has been studied repeatedly. The results obtained in geological reports and few published works are often poorly correlated with each other. Such a contradiction is caused by sampling for technological tests from different areas, which belong to two subformations, which have a number of differences. The age, stratigraphic position, and chemical and mineralogical features of the Tavda formation remain debatable and relevant issues, which requires additional study. A detailed study of the lithology of Tavda formation clays assumes importance in relation to the plans to expand the resource base and the need to re-profile the part of manufacturing capacity for the production of new commercial products. The main aim of the research is precise studies of material composition of the bulk samples from the lower and upper subformations of the Tavda formation Methods: field studies, X-ray diffraction, X-ray fluorescence analysis, determination of refractoriness, inductively coupled plasma mass spectrometry, scanning electron microscopy, lithological and petrographic analysis in thin sections. Results. The paper presents the results of the studies of chemical and mineralogical compositions, features of lithology and microstructure of clay rocks from the Kyshtyrlinskiy site (Tyumen region). Clay rocks have a certain variability of mineral composition: but the clay mica mixed-ayer-smectite matrix is constant. In the lower part, the clay rock mass is composed mainly of mica and mixed-layer illitesmectite formations. The upper subformation clays are more closely related to the kaolin-mica-montmorillonite type with admixtures of pyrite, silica, sulfates, carbonates and organic substances. The formation of such mixed-layer masses is probably due to degradation of detrital minerals and the primary clay substrate. The established distribution of rare earth elements indicates significant changes in the redox conditions of the marine basin at various stages of its existence. The studied clay is considered as bentonite-like.